fibers and ||= behaviour

output.txt

ruby-1.9.2-p180-fastrequire :001 > f = Fiber.new do
ruby-1.9.2-p180-fastrequire :002 >       @something ||= begin
ruby-1.9.2-p180-fastrequire :003 >           Fiber.yield # external query
ruby-1.9.2-p180-fastrequire :004?>         2
ruby-1.9.2-p180-fastrequire :005?>       end
ruby-1.9.2-p180-fastrequire :006?>   end
 => #<Fiber:0x000000028d45a8> 
ruby-1.9.2-p180-fastrequire :007 > f.resume
 => nil 
ruby-1.9.2-p180-fastrequire :008 > puts @something.inspect
nil
 => nil 
ruby-1.9.2-p180-fastrequire :009 > instance_variables
 => [:@prompt] 
ruby-1.9.2-p180-fastrequire :010 > f.resume
 => 2 
ruby-1.9.2-p180-fastrequire :011 > 
ruby-1.9.2-p180-fastrequire :012 >   instance_variables
 => [:@prompt, :@something] 
ruby-1.9.2-p180-fastrequire :013 > puts @something.inspect
2
 => nil 
ruby-1.9.2-p180-fastrequire :014 >